I know that a reason for wearing a black hat is because one must wear two layers covering their head (Mishna Brurah 91:5) but am wondering if that Din is based in Kabbalah?
http://www.hebrewbooks.org/pagefeed/hebrewbooks_org_26128_37.pdf He discusses it there and brings maharsha in shabbos 156b on the gemoro of why R Nachman's mother covered his head specially because she was warned that he would one day become a thief. He asks everyone has to cover his head otherwise because of the shchina. He replies that she gave it 'extra' covering. From this we learn that 'extra' covering gives more yiras shomaim and stops you even becoming a thief. This of course doesnt answer why it has to be black which is really no more than fashion. This could be one good answer for the question of why one has extra head coverings. See also the comments here.